Biggest German-Speaking Cities

Because this isn't about individual cities. That's the whole point of agglomerations. To group cities together. Especially in Germany where there's often not just one major city in a metropolitan area but many and often you can't even tell where one city ends and another begins. For example the Cologne and Düsseldorf area also includes Bonn, Leverkusen, Wuppertal etc.

Another good example is Mannheim which in itself only has 311 000 inhabitants but with the city of Ludwigshafen literally on the other side of the Rhine river as well as cities like Heidelberg, Speyer and Worms only a few kilometers away it makes sense to group them together.